Ventilators are used in a variety of settings. For example, in a hospital a patient may be ventilated as part of their medical care. In particular, ventilators are commonly provided in hospital intensive care units (ICUs).
Many of these ventilators use high pressure or compressed gas source for breath delivery. In addition to generating and delivering breaths to the patient, a high-end ventilator may include an integrated system implementation. With such an implementation, a ventilator system can include other patient care modalities like secretion management and high frequency ventilation etc. These modalities require both positive pressure and negative pressure in the system for effective implementation. For example, in high frequency positive pressure ventilation (HFPPV), positive pressure is generated from the high pressure, compressed, gas source and negative pressure is generated by a venturi system implementation.
For example, for an HFPPV implementation, the mean airway pressure (MAP) depends on the peak-to-peak amplitude of the positive pressure pulses. For higher frequencies or for higher amplitudes, the MAP may be too high for the patient. MAP can only be lowered by applying negative pressure during exhalation. This negative pressure may be generated by a venturi effect from the positive pressure side of the system. However, a venturi system is very noisy and it has a relatively slow response. In another modality such as secretion management, a ventilator system needs to deliver insufflation (positive pressure) and exsufflation (negative pressure) to simulate a cough. In yet another modality such as noninvasive ventilation incorporated in high-end ICU ventilators, a blower can additionally augment and/or provide higher flows of gas that may be needed for such ventilation therapy. The gas supplied from individual gas outlets in the hospitals may be limited to ˜180 liters per minute (lpm) and is adequate for the most invasive mechanical ventilation needs. However, for non-invasive ventilation, the ventilator should be able to generate much higher flows—on the order of 250 to 300 liters/minute (lpm) to compensate for mask leaks.
Accordingly, it would be desirable to provide a ventilator and method of ventilation which can address one or more of these requirements.
In one aspect of the invention, a ventilator system comprises: an inspiration port configured to be connected to an inspiratory limb of a dual-limb patient circuit, and an expiration port configured to be connected to an expiratory limb of the dual-limb patient circuit; a gas delivery device operatively connected to the inspiration port and configured to supply a pressurized flow of gas to the inspiration port to generate positive pressure; and a blower having an inlet that is operatively connected to the expiration port and configured to be controlled to selectively supply a negative pressure level between 4 and 120 cmH2O to the expiratory limb, and further having an outlet configured to exhaust gas received via the expiration port.
In another aspect of the invention, a method of ventilation comprises: providing an inspiration port configured to be connected to an inspiration limb of a dual-limb patient circuit, and providing an expiration port configured to be connected to an expiratory limb of the dual-limb patient circuit; supplying a pressurized flow of gas to the inspiration port to generate positive pressure; and selectively connecting an inlet of a blower to the expiration port to selectively supply a negative pressure level between 4 and 120 cmH2O to the expiration port and to exhaust from an outlet of the blower gas received from the expiration port.
In yet another aspect of the invention, a ventilator system comprises: a patient circuit interface port configured to be connected to a single-limb patient circuit; a gas delivery device operatively connected to the patient circuit interface port and configured to supply a pressurized flow of gas to the patient circuit interface port to generate positive pressure; a blower having an outlet operatively connected to the patient circuit interface port and configured to supply a pressurized flow of air to the patient circuit interface port to generate positive pressure; a pressure transducer configured to measure a patient airway pressure; at least one flow sensor configured to measure a gas flow in the patient circuit; and a controller configured to control the gas delivery device and the blower in response to a pressure transducer signal indicating the measured pressure in the patient circuit and a flow sensor signal indicating the measured gas flow from the gas delivery device.